Semiconductor device and method of manufacturing the same

ABSTRACT

A plurality of solar batteries are provided between a first substrate and a second substrate. The first substrate and the second substrate are formed of, for example, a paper or a non-woven cloth, which is a material including a natural fiber, cellulose, as the main component. Papers and silicon have relatively small difference in coefficient of thermal expansion so that warp caused by changes in the temperature is suppressed. Also, papers are light, easy to be processed and spontaneously decomposed so that disposing becomes easy. The first substrate is preferable to be transparent or semitransparent and preferable to be formed of cellophane paper, glassine paper, parchment paper, or Japanese paper. Oil may be included in the material. The second substrate is preferable to be opaque. A waterproof film may be formed on the first substrate and the second substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device comprising thinfilm semiconductor layers such as a solar battery and a method ofmanufacturing the same. Specifically, it relates to a semiconductordevice manufactured through forming thin film semiconductor layers on aprovisional substrate and then transcribing it on another substrate, anda method of manufacturing the same.

2. Description of the Related Art

In recent years, solar batteries have come to be in practical use. It isnecessary to save resources and to decrease costs to utilize solarbatteries in full-scale. Thin film solar batteries are preferred tothick film solar batteries when energy conversion (light-electricity)efficiency and shortening the cycle of energy recycle are taken intoconsideration.

The same applicants as this application have first proposed a method ofseparating an element formation layer from a substrate (Japanese PatentApplication laid-open Hei 8-213645). In the method, a porous layer isformed on a single crystalline substrate as an isolation layer and asemiconductor layer to be a solar battery is grown on the porous layer.Then, a plastic plate or a glass plate is adhered onto the semiconductorlayer using an adhesive, and the semiconductor layer is exfoliated fromthe single crystal substrate together with the plastic plate or theglass plate by applying tensile stress.

As described, a thin film solar battery of the related art ismanufactured by transcribing it onto a plastic plate or a glass plate.As a result, warp is generated because of the difference in thermalexpansion of the solar battery and the plastic plate, resulting in thedestruction of the solar battery. Also, a glass plate is difficult to beapplied depending on its usage since it is hard to be folded or to becut.

Furthermore, as the plastic plate and the glass plate are notspontaneously decomposed, the solar battery which becomes unusable mustbe artificially decomposed when being disposed. Therefore, there is aproblem of waste disposal such as running cost of decomposing, if solarbatteries becomes widespread use in full-scale, and if there are a largeamount of the solar batteries which are unusable.

SUMMARY OF THE INVENTION

The invention has been designed to overcome the forgoing problems. Theobject is to provide a semiconductor device in which warp is suppressedand processing and disposing can be easily performed, and a method ofmanufacturing the same.

A semiconductor device of the invention comprises: thin filmsemiconductor layers having one side and the other side facing eachother;

and a first substrate made of a material including cellulose which ispositioned on the one side.

A method of manufacturing a semiconductor device of the inventionincludes the steps of: depositing thin film semiconductor layers on aprovisional substrate; exfoliating the thin film semiconductor layersfrom the provisional substrate; and transcribing the thin filmsemiconductor layers onto the first substrate.

In the semiconductor device of the invention, the first substrate isformed of a material containing cellulose. Therefore, the difference inthermal expansion of the first substrate and the thin film semiconductorlayers is decreased and warp caused by changes in temperature issuppressed. Also, the semiconductor device becomes light and processingbecomes easy. Furthermore, the thin film semiconductor layer can bespontaneously decomposed so that disposal becomes easy.

In the method of manufacturing a semiconductor device of the invention,after thin film semiconductor layers are deposited on a provisionalsubstrate, the thin film semiconductor layers are exfoliated from theprovisional substrate; and the thin film semiconductor layers aretranscribed onto the first substrate.

Other and further objects, features and advantages of the invention willappear more fully from the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section showing the configuration of a semiconductordevice according to a first example of the invention.

FIGS. 2A, 2B, 2C and 2D are cross sections showing each manufacturingstep of the semiconductor device shown in FIG. 1.

FIGS. 3A, 3B and 3C are cross sections showing each manufacturing stepfollowing the steps shown in FIGS. 2A, 2B, 2C and 2D.

FIGS. 4A and 4B are cross sections showing each manufacturing stepfollowing the steps shown in FIGS. 3A, 3B and 3C.

FIG. 5 is a cross section showing the configuration of a semiconductordevice according to a second example of the invention.

FIG. 6 is a cross section showing the configuration of a semiconductordevice according to a third example of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Examples of the invention will be described in the followings withreference to the drawings.

FIRST EXAMPLE

FIG. 1 shows the configuration of a semiconductor device according to afirst example of the invention. The semiconductor device comprises aplurality of solar batteries 10, which are thin film semiconductorlayers, provided with a space in between each of them. FIG. 1 shows twoof the solar batteries. The solar batteries 10 have one side and theother side facing each other. A first substrate 21 for both of the solarbatteries 10 is extendedly formed on one side and a second substrate 22for both is extendedly formed on the other side, respectively. The solarbatteries 10 and the first substrate 21 are adhered by an adhesive layer23 while the solar battery and the second substrate 22 are adhered by anadhesive layer 24. The adhesive layers 23 and 24 are made of ethylenevinyl acetate (EVA), phloro plastic (THV) or the like.

Each of the solar batteries 10 has the same configuration, comprising asemiconductor layer 11 of about 1 to 50 μm in thickness made of singlecrystalline silicon. Each of p-type regions 11 a of 1 to 49 μm inthickness including p-type impurity such as boron (B) 1×10¹⁵ to1×10¹⁸/cm³ is provided in each of the semiconductor layers 11.

Each of n⁺-type regions 11 b of about 0.2 μm, for example, in thickness,including n-type impurities such as phosphorus (P) with highconcentration such as 1×10¹⁹/cm³, is provided on one side (that is, thefirst substrate 21 side) adjacent to each of the p-type regions 11 a.Furthermore, each of p⁺-type regions 11 c of about 1 μm, for example, inthickness including p-type impurity such as boron with highconcentration such as 1×10¹⁹/cm³, is provided on one side of each of thep-type regions 11 a. Each of the n⁺-type regions 11 b, which is cathodeof the solar battery, and each of the p⁺-type regions 11 c, which isanode of the solar battery, are provided with a space in between in eachof the semiconductor layers 11.

Each of p⁺-type regions 11 d of about 1 μm, for example, in thickness,including p-type impurities such as boron with high concentration suchas 1×10¹⁹/cm³, is provided on the other side (that is, the secondsubstrate 22 side) adjacent to each of the p-type regions 11 a. Thep⁺-type regions 11 d are for reflecting electron generated by light inthe p-type regions 11 c and for increasing light-electric conversionefficiency by decreasing recombination of electron and hole in thep⁺-type regions 11 d.

Each of the solar batteries 10 comprises a reflection-proof film 12 eachprovided on one side of each semiconductor layer 11. Each of thereflection-proof films 12 is formed of, for example, titanium oxide(TiO₂) of about 60 nm in thickness and prevent light from beingreflected from the surface (especially, the surface of each of n⁺-typeregions 11 b) of each semiconductor layer 11. An opening is formed ineach of the reflection-proof films 12 corresponding to each of then⁺-type regions 11 b, and each of metallic electrodes 13 made ofaluminum (Al), for example, is electrically connected to each of then⁺-type regions 11 b through each opening.

Each of the metallic electrodes 13 is extended to a neighboring solarbattery 10, respectively, and is electrically connected to each of thep⁺-type regions 11 c through the opening formed on each reflection-prooffilm 12. In other words, each of the metallic electrodes 13 connects twoneighboring solar batteries 10 in series. An oxidation film 14 is formedin between each metallic electrode 13 and each semiconductor layer 11,respectively. Each of the metallic electrodes 13 is electricallyconnected to each of the n⁺-type regions 11 b and each of the p⁺-typeregions 11 c, respectively, through each opening formed on the oxidationfilm 14.

Each of the solar batteries 10 further comprises a reverse-sideelectrode 15 provided adjacent to the other side of each of p⁺-typeregions 11 d. Each of the reverse-side electrodes 15 is formed ofaluminum, for example, and decreases series resistance of each solarbattery 10 while reflecting the light permeated through thesemiconductor layer 11.

The first substrate 21 and the second substrate 22 have a thickness ofabout 100 μm, for example, and are made of at least paper or non-wovencloth, for example, which includes a natural fiber, cellulose, as themain component. It is preferable that the first substrate 21 istransparent or semitransparent in order to increase permeation rate oflight. This means, it is preferable that the first substrate 21 isformed of at least one kind of paper selected from the group ofcellophane paper, glassine paper, parchment paper (paper which is madeof chemical pulp and is processed by sulfuric acid solution), andJapanese paper such as shoji paper, for example. Paper or non-wovencloth including oil are also preferable as the material for the firstsubstrate 21 since they have high permeation rate. On the other hand, itis preferable that the second substrate 22 is opaque, highly lustrousand white in order to increase the reflection rate of light.

There is a case where at least part of the surfaces of the firstsubstrate 21 and the second substrate 22 have patterns of illustrationsor letters, which can be marks for distinguishing or can add the beautywhen they are in use. The patterns may be formed by makingconcavo-convex area on the surface or may be formed by printing.

Such semiconductor device can be manufactured as follows.

FIGS. 2A, 2B, 2C, 2D to FIGS. 4A, 4B show each manufacturing step.First, as shown in FIG. 2A, a provisional substrate 31 having, forexample, a plurality of solar battery forming regions 31 a is provided.The provisional substrate 31 is formed of single crystalline siliconhaving a specific resistance of about 0.01 to 0.02 Ω· cm to which p-typeimpurity such as boron is added. Next, as shown in FIG. 2B, a porouslayer 32 is formed on the surface of the provisional substrate 31 byanodizing, for example.

Anodizing is a method of performing energizing using the provisionalsubstrate 31 as anode in hydrofluoric acid solution. It can be performedby double-cell method, for example, disclosed in “‘Anodizing of poroussilicon’ Surface Technology Vol. 46 No. 5 p8-13, 1995” by ITO and someothers. In this method, a silicon substrate 31 on which a porous siliconlayer 32 is formed is positioned in between two electrolytic solutioncells, and a platinum electrode which is connected to the direct-currentpower supply is provided in each of both electrolytic solution cells.Then electrolytic solution is supplied to both of the electrolyticsolution cells and direct-current voltage is applied to the platinumelectrode. Thereby, the silicon substrate 31 becomes anode and theplatinum electrode becomes cathode. As a result, one of the surface ofthe silicon substrate 31 is eroded and becomes porous.

At this time, a first porous layer with a low porous rate is formed byperforming a first step of anodizing for eight minuets with currentdensity of about, for example, 0.5 to 3.0 mA/cm² using, for example,electrolytic solution of HF (hydrogen fluoride): C₂H₅OH (ethanol)=1:1 aselectrolytic solution (anodizing solution). Then, a second porous layerwith medium porous rate is formed by performing a second step ofanodizing for eight minutes with current density of about, for example,3 to 20 mA/cm². A third porous layer with high porous rate is formed byperforming a third step of anodizing for several seconds with currentdensity of about, for example, 40 to 300 mA/cm². Incidentally, the thirdporous layer is the base for an isolation layer 32 a (FIG. 2C) which isdescribed later. Thereby, a porous layer 32 having a total thickness ofabout 8 μm is formed.

It is preferable that the provisional substrate 31 made of p-type singlecrystalline silicon is used since the porous silicon layer is formedthereon by anodizing. However, the substrate made of n-type singlecrystalline silicon or polycrystalline silicon may be used depending onthe condition.

Then, each of the solar batteries 10 is formed on the porous layer 32.First, holes on the surface of the porous layer 32 are covered byperforming hydrogen annealing for thirty minutes at, for example, 1100°C. Then, as shown in FIG. 2C, p⁺-type regions 11 d and p-type regions 11a, each of those made of single crystalline silicon are formed on, forexample, the porous layer 32 in order by epitaxial growth using gas suchas silane (SiH₄) at 1070° C.

While performing hydrogen annealing and epitaxial growth, atoms ofsilicon in the porous layer 32 are moved and rearranged. As a result,the portion of the porous layer 32, which has high porous rate furtherincreases the porous rate and a layer with the least strength intensile, that is, an isolation layer 32 a is formed. However, theisolation layer 32 a has sufficient tensile strength to an extent thatthe whole or a part of the p⁺-type regions 11 d and the p-type regions11 a do not exfoliate from the provisional substrate 31 when formingeach of the solar batteries 10 on the porous layer 32.

Next, as shown in FIG. 2D, an oxidation film 33 is selectively formed onthe p-type regions 11 a which corresponds to each of the solar batteryforming regions 31 a by CVD (Chemical Vapor Deposition) method. Then,the p-type regions 11 a and the p⁺-type regions 11 d are selectivelyremoved in order using, for example, alkaline etching solution such aspotassium hydroxide (KOH) using the oxidation film 33 as a mask.Thereby, the p-type regions 11 a and the p⁺-type regions 11 d areseparated, respectively, in accordance with each of the solar batteryforming regions 31 a, and are separated to each of the solar batteries10.

At this time, etching may be performed until the porous layer 32 inorder to ensure the separation of each of the solar batteries 10.However, it is preferable that etching is not performed until theisolation layer 32 a in order to exfoliate the solar batteries 10 easilyfrom the provisional substrate 31 in the step to be described later.

After separating the p-type regions 11 a and the p⁺-type regions 11 d,respectively, as shown in FIG. 3A, the oxidation film 33 is selectivelyremoved in accordance with regions which each p⁺-type region 11 d isformed so that the surfaces of the corresponding p-type regions 11 a areselectively exposed. Then, each p⁺-type region 11 c is formed byinjecting p-type impurity such as boron with high concentration intoeach p-type regions 11 a by, for example, ion implantation. Afterforming each of the p⁺-type regions 11 c, an oxidation film is formedthereon by CVD method or thermal oxidation. An oxidation film 14 isformed of this oxidation film and the oxidation film 33 formed earlier.

After forming the oxidation film 14, as shown in FIG. 3B, the oxidationfilm 14 is selectively removed in accordance with region which eachn⁺-type region 11 b is formed so that the surfaces of the correspondingp-type regions 11 a are selectively exposed. Then, n⁺-type regions 11 bare formed by injecting n-type impurity such as phosphorous with highconcentration into each p-type region 11 a by, for example, ionimplantation. After forming each of the n⁺-type regions 11 b, areflection-proof film 12 is formed all over the surface and an openingis selectively formed on the reflection-proof film 12 and the oxidationfilm 14, respectively, in accordance with each n-type region 11 b andeach n⁺-type region 11 c. Then, each of metallic electrodes 13 made of,for example, aluminum is selectively formed so as to, for example,connect each of the neighboring solar batteries in series.

After forming each of the solar batteries 10, as shown in FIG. 3C, afirst substrate 21 made of a material which includes cellulose as themain component is adhered onto one side of each solar battery 10 withthe contact layer 23 in between.

After adhering the first substrate 21, as shown in FIG. 4A, each of thesolar batteries 10 is exfoliated from the provisional substrate 31together with the first substrate 21 in the isolation layer 32 a, and istranscribed onto the first substrate 21, respectively. At the time ofexfoliating the solar batteries 10, for example, one of, or acombination of two or three of the following three methods are used: oneis a method of adding tensile stress onto the first substrate 21 and theprovisional substrate 31; another is a method of soaking the provisionalsubstrate 31 in water or solution of such as ethanol and decreasing thestrength of the isolation layer 32 a by irradiating supersonic; and theother is a method of decreasing the strength of the isolation layer 32 aby adding centrifugal separation. In the method of irradiatingsupersonic, if supersonic of, for example, 25 kHz, 600 W is irradiated,energy of supersonic is effectively transmitted to each solar battery 10and the first substrate 21 so that atoms of silicon in the porous layer32 are cut. As a result, tensile strength of the isolation layer 32 a isremarkably decreased.

After transcribing each of the solar batteries 10 onto the firstsubstrate 21, as shown in FIG. 4B, the porous layer 32 remained on theother side of each p⁺-type region 11 d is removed using alkaline etchingliquid such as potassium hydroxide. Thereby, each of the neighboringsolar batteries 10 which is short-circuited by the porous layer 32 iscompletely isolated. Then, each reverse-side electrode 15 made ofaluminum is formed on the other side of each p⁺-type region 11 d by, forexample, printing method.

At last, a second substrate 22 made of a material which includescellulose as the main component is adhered onto each solar battery 10 onthe opposite side (that is, the other side) of the first substrate 21with a contact layer 24 in between. Thereby, a semiconductor deviceshown in FIG. 1 is completed.

The provisional substrate 31 after the solar batteries 10 are exfoliatedcan be reused in the next step of forming solar batteries provided thatthe porous layer 32 which is remained on the surface is removed byetching.

The semiconductor device manufactured as described operates as follows.

In the semiconductor device, if light is irradiated, part of lightpermeates through the first substrate 21 into each solar battery 10 andis absorbed. In each n⁺-type region 11 b and each p-type region 11 a inwhich light is absorbed, an electron-hole is generated. The electrongenerated in each of the p-type regions 11 a is pulled by electric fieldand moves into each of the n⁺-type regions 11 b, and the hole generatedin each of the n⁺-type regions 11 b is pulled by electric field andmoves into each of the p-type regions 11 a. Thereby, electric currentproportional to the amount of irradiation light is generated.

In the semiconductor device, the first substrate 21 is made of amaterial which includes cellulose as the main component so thatirradiation of light into each of the solar batteries 10 is secured.Especially, if the first substrate 21 is transparent or semitransparent,sufficient amount of irradiation light is obtained.

Furthermore, the first substrate 21 and the second substrate 22 are madeof a material which includes cellulose as the main component,respectively, so that the difference in coefficient of thermal expansionbetween the first substrate 21, the second substrate 22 and each solarbattery 10 can be decreased and warp caused by changes in thetemperature can be suppressed. As a result, breakdown of each solarbattery 10 can be suppressed.

According to the example, the difference in coefficient of thermalexpansion between the first substrate 21, the second substrate 22 andeach solar battery 10 can be decreased and warp caused by changes in thetemperature can be suppressed since the first substrate 21 and thesecond substrate 22 are made of a material which include cellulose asthe main component, respectively. As a result, breakdown of each solarbattery 10 can be suppressed.

In addition, the semiconductor device can be lightened and the cost canbe decreased while processing such as folding, bending, adhering orcutting can be easily performed. Therefore, its usage can be largelyexpanded to a case where, for example, the semiconductor device isbuilt-in as the electric source of a watch.

Furthermore, it can be spontaneously decomposed so that the cost neededfor disposing can be decreased. Also, a toxic environmental hormone doesnot generate so that the environment can be protected. In addition,illustrations or letters can be drawn on the surfaces of the firstsubstrate 21 and the second substrate 22. Therefore, the appearance whenit is in use can be improved adding to its value.

Moreover, if the first substrate 21 is transparent or semitransparent,the amount of light irradiated into each of the solar batteries 10 canbe increased and the efficiency can be improved. In addition, if thesecond substrate 22 is opaque, light passed through each solar battery10 can be reflected so that the amount of light irradiated into eachsolar battery 10 can be increased. As a result, efficiency of each solarbattery 10 can be improved.

SECOND EXAMPLE

FIG. 5 shows the configuration of a semiconductor device according to asecond example of the invention. The semiconductor device has theidentical configuration, operation and effects to those of the firstexample except that it comprises a reflection film 45. Also, it can beformed like the first embodiment. Hence, like elements are given likenumerals and the detailed description of them will be omitted.

The reflection film 45 is made of titanium oxide and is formed on thesecond substrate 22 on the solar batteries 10 side. The reflection film45 is for increasing the amount of light irradiated into each solarbattery 10 by reflecting the light passed through each solar battery 10.At this time, although the reflection film 45 is formed on the secondsubstrate 22 on the solar batteries 10 side, it may be formed on thesecond substrate 22 on the opposite side of the solar batteries 10.Also, although the reflection film 45 is formed all over the surface, itmay be formed on part of the surface. Incidentally, if the reflectionfilm 45 is provided, the second substrate 22 does not required to beopaque, unlike the first example. The reflection film 45 can be formedby applying the powder of titanium oxide onto the surface of the secondsubstrate 22.

According to the example, the light passed through each of the solarbatteries 10 can be reflected since the reflection film 45 is included.As a result, the amount of light irradiated into each solar battery 10can be increased. Therefore, efficiency of each solar battery 10 can beimproved.

THIRD EXAMPLE

FIG. 6 shows the configuration of a semiconductor device according to athird example of the invention. The semiconductor device has theidentical configuration, operation and effects to those of the firstexample except that it comprises waterproof films 56 and 57. Also, itcan be formed in the same manner as in the first example. Therefore,like elements are given like numerals and the detailed description ofthem will be omitted.

The waterproof film 56 is formed, for example, on the first substrate 21on the opposite side of the solar batteries 10, and the waterproof film57 is formed, for example, on the second substrate 22 on the oppositeside of the solar batteries 10. The waterproof films 56 and 57 have athickness of 20 μm, for example, and it is preferable that they areformed of resin film, respectively. As resin used for the resin film,for example, the following will be suitable: polyolefin resin; polyesterresin; melamine resin; silicon resin; or biodegradable resin such aspolylactic acid. The waterproof films 56 and 57 are for preventing thefirst substrate 21 and the second substrate 22 from absorbing water andswelling.

At this time, the waterproof film 56 is formed on the first substrate 21on the opposite side of the solar batteries 10 and the waterproof film57 is formed on the second substrate 22 on the opposite side of thesolar batteries 10. However, the waterproof film 56 may be formed onboth sides of the first substrate 21 and the waterproof film 57 may beformed on both sides of the second substrate 22. In addition, althougheach of the waterproof films 56 and 57 are formed all over each of thefirst substrate 21 and the second substrate 22 at this time, they may beformed on a part of those surfaces.

If necessary, a waterproof film made of resin may be formed on at leasta part of the end face of the first substrate 21 and the secondsubstrate 22 in order to prevent the first substrate 21 and the secondsubstrate 22 from being impregnated with water. In addition, ifnecessary, a waterproof film such as a resin may be added to at least apart of the first substrate 21 and the second substrate 22. As a resincomposing the waterproof film or the waterproof substance, thefollowings are used: emulsion such as polyolefin or synthetic rubber;polyester resin; melamine resin; silicon resin; or biodegradable resin.Especially, it is preferable that the resin having about the same indexof refraction as cellulose is used when the first substrate 21 isimpregnated with a resin so that the first substrate 21 can be made moretransparent.

According to the example, the first substrate 21 and the secondsubstrate 22 can be prevented from absorbing water and swelling sincethe waterproof films 56 and 57 are included in the device. As a result,breakdown of the solar batteries 10 by swelling can be suppressed.

Although the invention has been described by referring to each of theexamples, it is not limited to the above-mentioned examples but variousmodifications can be applicable. For example, although a case where thefirst substrate 21 and the second substrate 22 are formed of at leasteither paper or non-woven cloth has been described in theabove-mentioned examples, they may be formed of a material in whichpaper and non-woven cloth are laminated. Also, they may be formed of amaterial in which a plurality of papers are laminated. In this case, itis preferable that papers are laminated by making the flow direction ofthe fiber of cellulose generated at the time of making papers parallelor orthogonal.

Furthermore, although a case where the whole first substrate 21 istransparent or semitransparent has been described in the above-mentionedexamples, only a part of it corresponding to each of the solar batteries10 may be transparent or semitransparent. Also, if the first substrate21 is formed of paper or non-woven cloth including oil, only a part ofthe first substrate 21 corresponding to each of the solar batteries 10may be formed by that material.

In addition, although a case where the whole second substrate 22 isopaque has been described in the above-mentioned examples, only a partof it corresponding to each of the solar batteries 10 may be opaque.

Furthermore, although a case where the semiconductor layer 11 is formedof single crystalline silicon has been described in the above-mentionedexamples, it may be formed of polycrystalline silicon, amorphoussilicon, the complex of both or a composite layer of both. In addition,in the above-mentioned examples, although the configuration of eachsolar battery 10 is described by referring to a specific example, theinvention is broadly applied to a semiconductor device comprising solarbatteries having another configuration.

Moreover, a case where the semiconductor device comprises solarbatteries 10 as thin film semiconductor layers has been described in theabove-mentioned examples. However, the invention is broadly applied to acase where the semiconductor device comprises other thin filmsemiconductor layers such as other light-absorbing element or emissionelement, liquid crystal display, or integrated circuit element.

As described, a semiconductor device of the invention comprises a firstsubstrate made of a material including cellulose. As a result, thedifference in thermal expansion of the first substrate and thin filmsemiconductor layers can be decreased and warp caused by changes in thetemperature can be suppressed. Therefore, breakdown of the thin filmsemiconductor layers can be suppressed.

Furthermore, the semiconductor device can be lightened and the cost canbe decreased while processing such as folding, bending, adhering orcutting can be easily performed. Also, it can be spontaneouslydecomposed so that the cost needed for disposing can be decreased. Also,a toxic environmental hormone does not generate so that the environmentcan be protected.

Especially, if solar batteries are included as the thin filmsemiconductor layers, the amount of light irradiated into each of thethin film semiconductor layers can be increased and the efficiency canbe improved since the first substrate is formed to be transparent orsemitransparent.

In addition, by drawing illustrations on at least a part of the firstsubstrate 21, the appearance can be improved adding to its value when itis in use.

Furthermore, the first substrate and the second substrate can beprevented from absorbing water and swelling by comprising a waterprooffilm or including a waterproof substance. As a result, breakdown of thethin film semiconductor layers by swelling can be suppressed.

Moreover, by comprising a second substrate made of a material includingcellulose, same effect as comprising the first substrate made of amaterial including cellulose can be obtained.

In addition, the light passed though the thin film semiconductor layerscan be reflected, and the amount of the light irradiated into the thinfilm semiconductor layers can be increased in a case where the solarbatteries are included as the thin film semiconductor layers by makingthe second substrate opaque or comprise a reflection film. As a result,efficiency can be increased.

Moreover, according to a method of manufacturing a semiconductor deviceof the invention, the semiconductor device of the invention can beeasily manufactured since the thin film semiconductor layers areexfoliated from the provisional substrate and are transcribed onto thefirst substrate made of a material including cellulose.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. A semiconductor device comprising: thin filmsemiconductor device layers having one side and the other side facingeach other; and a first substrate made of a material includingcellulose, which is positioned on the one side; wherein at least a partof the first substrate includes oil.
 2. A semiconductor devicecomprising: thin film semiconductor device layers having one side andthe other side facing each other; a first substrate made of a materialincluding cellulose, which is positioned on the one side; and a secondsubstrate made of a material including cellulose, which is positioned onthe other side of the thin film semiconductor layers.
 3. A semiconductordevice according to claim 2 wherein the second substrate contains paperand/or non-woven cloth.
 4. A semiconductor device according to claim 2wherein at least a part of the second substrate is opaque.
 5. Asemiconductor device according to claim 2 wherein a reflecting film isdeposited on at least a part of the surface of the second substrate. 6.A semiconductor device according to claim 2 wherein at least a part ofthe surface of the second substrate is covered with a waterproofingfilm.
 7. A semiconductor device according to claim 2 wherein at least apart of the second substrate contains a waterproofing substance.